pH and total acidity are not the same thing

Both numbers appear on technical sheets and they are constantly conflated, including in otherwise careful wine writing.

Total acidity is expressed in grams per litre, usually as tartaric acid equivalent, and it broadly tracks what a taster registers as sourness.

pH is a logarithmic scale of hydrogen ion activity. Wine typically sits between about 3.0 and 4.0, and each whole point is a tenfold difference.

The two can move independently because acids in wine are partly neutralised by potassium taken up from the soil. A wine can carry a high total acid load and still have a relatively high pH if there is plenty of potassium present to buffer it.

This is not a curiosity. pH governs microbiological stability, how effective a given addition of sulfur dioxide will be, and colour stability in red wine — anthocyanins are more strongly coloured at lower pH.

A winemaker therefore watches pH for stability and total acidity for taste, and they may require different interventions.

Potassium uptake tends to rise with vine vigour and with certain rootstocks, and is generally higher in warm conditions, which is one reason warm-region wines can be both low in perceived freshness and awkward to stabilise.

It explains why acidification is not simply "adding sharpness": lowering pH is often the actual objective, and the taste consequence is a side effect.

It also explains why a red wine at high pH can look brownish and dull while a low-pH wine of the same age looks vivid.